2. What is a touch screen?
• An electronic visual
display that locates the
coordinates of a users
touch within display
area
• Works independently of
what is being
displayed on screen[7]
3. When is it Applicable?
• It allows users to interact directly
with what is being displayed,
rather than indirectly using a
mouse or keyboard
• Can be used without any
intermediate device
• Found in modern smartphones,
video games, kiosks, navigation
systems, etc. . .
[1]
4. Brief History
• Invented by E.A. Johnson (Royal
Radar Est.) around 1965 for air
traffic control
• HP-150 home computer using
infrared technology in 1983
• 1993 Apple’s Newton and
IBM’s Simon
• 2002 Microsoft’s Windows XP Tablet
• 2007 Apple’s iPhone (Multi-touch)
[6]
5. Touch Screen Technology
• Four different technologies used to make touch screens
today:
• Resistive
• Capacitive
• Surface Acoustic Wave (SAW)
• Infrared LED or Optical
6. Resistive Touch Screens
• Two layers of conductive
material
• Touch creates contact
between resistive layers
completing circuit
[2]
7. Resistive Touch Screens
• Voltage in circuit changes
based on position
• Controller determines
location based on voltages
• Any material can trigger
sensors
[2]
8. Why Resistive?
• Advantages:
• Cost-effective and low power Requirements
• Activated by any object
• Accurate
• Disadvantages:
• Polyester surface can be damaged
• Only 75% light transmission
• Lower endurance (~35 million touches)
9. Resistive
Summary
• 8” resistive touch screen will cost about $60
• 4 and 5 wire touch screens don’t need controllers
• For those that do, they cost less than $5
• Any object can be used to activate the screen
• Not able to register multiple touches
• ~75% of light is transferred through (12.5% per layer)
10. Capacitive Touch Screens
• Glass panel with conductive
layer (Indium Tin Oxide)
• Small amount of voltage
applied to four corners of
touch screen
[2]
11. Capacitive Touch Screens
• Touch draws minute
amount of current creating
voltage drop
• Coordinates of point of
contact calculated by
controller
[2]
12. Why Capacitive?
• Advantages:
• Durable surface material
• High endurance (~255 million touches)
• Very accurate
• Good optical quality
• Disadvantages:
• Triggered only by bare finger or active stylus
13. Capacitive
Summary
• 8” capacitive touch screen costs about $100
• Controllers can be bought for less than $5
• Only conductive objects can be used to activate
• Able to register multiple touches
• ~88% of light is transferred through
14. Surface Acoustic Wave Touch
Screens
• Surface consists of glass overlay with transmitting
and receiving transducers
[2]
15. Surface Acoustic Wave Touch
Screens
• Electrical signals sent to the transmitting transducers
converts to ultrasonic waves
• Waves are directed across screen by reflectors then
directed to receiving transducers
[2]
16. Surface Acoustic Wave Touch
Screens
• When finger touches screen it absorbs waves
• Received values are compared to stored digital
maps to calculate x and y coordinates
[2]
17. Why SAW?
• Advantages:
• Best optical quality
• High surface durability and seal
• Activated by multiple sources
• Disadvantages:
• Expensive
• Contaminates on screen can cause false-touches
18. Surface Acoustic Wave
Summary
• We were not able to find prices for individual screens
• Any object can be used to activate the screen
• Able to register multiple touches
• ~100% of light is transferred through
21. Infrared/Optical
Touch Screens
• Advantages:
• High optical clarity
• Durable surface
• Supports multi-touch
• Can scale to large sizes
• Disadvantages:
• Expensive
• Cameras can get out of alignment
22. Infrared/Optical
Summary
• 8” infrared touch screen costs about $160
• Any object can be used to activate the screen
• Able to register multiple touches
• ~100% of light is transferred through
23. Type Examples Price (DigiKey) Tool for Input Multi-touch
Resistive
$10 (3.5”)
$60 (8”)
$150 (19”)
Any object No
Capacitive
$100 (8”)
$160 (19”)
$310 (32”)
Finger or
active stylus
Yes
SAW
$500 (15”)
$850 (19”)
*includes touch screen and
LCD monitor
Any object Yes
Infrared/
Optical
$130 (8”)
$250 (19”)
$320 (26”)
Any object Yes
[1]
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![What is a touch screen?
• An electronic visual
display that locates the
coordinates of a users
touch within display
area
• Works independently of
what is being
displayed on screen[7]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)